please explain how they worked out the closeness rating? and if there is a standard formula to be used. kindly open platform for discussion so I understand fully

A college office building has five departments: A (accounting office), B (bursar's office), C (credit department), D (data processing department), and E (educational support services). Paper forms are routed for processing through these departments in the quantities and sequences indicated in the table below. (a) Based on these data, construct the from-to chart. (b) Develop the activity relationship chart for these five departments, given that the from-to chart is the only basis for it. Solution: (a) From-to chart and (b) activity-relationship chart. To determine the closeness ratings in (b), the following divisions were used: "A" = number of trips 5; " "E" = number of trips =35 to 49 ; "l" = number of trips =20 to 34 ; "O" = number of trips =1 to 19 , and "U" = zero trips. A college office building has five departments: A (accounting office), B (bursar's office), C (credit department), D (data processing department), and E (educational support services). Paper forms are routed for processing through these departments in the quantities and sequences indicated in the table below. (a) Based on these data, construct the from-to chart. (b) Develop the activity relationship chart for these five departments, given that the from-to chart is the only basis for it. Solution: (a) From-to chart and (b) activity-relationship chart. To determine the closeness ratings in (b), the following divisions were used: "A" = number of trips 5; " "E" = number of trips =35 to 49 ; "l" = number of trips =20 to 34 ; "O" = number of trips =1 to 19 , and "U" = zero trips